Method and circuit for analyzing and reconstructing current type digital active EMI (Electro-Magnetic Interference) filtering based on switching spectrum

Abstract

The invention relates to a method and circuit for analyzing and reconstructing current type digital active EMI filtering based on a switching frequency spectrum, and the method comprises the steps: obtaining initial common-mode noise data and initial differential-mode noise data of a Buck circuit at a switching frequency point; constructing a common-mode equivalent circuit and a differential-mode equivalent circuit comprising a noise source, a compensation voltage source, a compensation capacitor, a parasitic capacitor and LISN impedance, and calculating initial compensation voltage common-mode data and initial compensation voltage differential-mode data of each frequency point to obtain initial compensation voltage data; synchronously outputting the initial compensation voltage data through a DAC (Digital-to-Analog Converter), and performing initial noise compensation; and measuring noise voltage on the LISN as noise source voltage, calculating to obtain secondary compensation voltage data, and carrying out superposition iteration on the compensation voltage data. The method is suitable for a scene with common-mode noise as a main part, can realize common-mode and differential-mode composite suppression without detection and size reduction, and continuously optimizes an EMI suppression effect through iterative updating.

Description

Technical Field

[0001] The present application relates to the technical field of EMI suppression of power electronic converters mainly based on common mode noise, and in particular to a current-type digital active EMI filtering method and circuit based on switching spectrum analysis and reconstruction. Background Art

[0002] At present, power electronics technology is developing rapidly, and power electronic converters are increasingly widely used in new energy, electric vehicles, industrial control and other fields. With the popularization of wide bandgap semiconductor devices (such as SiC and GaN), converters are driven to develop in the direction of high switching frequency and high power density. However, high switching frequency can easily lead to higher voltage change rate (dv / dt) and current change rate (di / dt), as well as stronger electromagnetic coupling between components, further exacerbating the electromagnetic interference (EMI) problem of power electronic converters.

[0003] In the face of electromagnetic interference from power electronic converters, EMI filters are usually used to suppress it. Traditional EMI filters are divided into two types: passive and active. Among them, passive EMI filters are composed of passive devices such as inductors and capacitors, which can suppress electromagnetic interference, but their size is large and it is difficult to adapt to the needs of high power density. Active EMI filters detect the electromagnetic interference voltage or current generated by the power electronic converter, amplify it through an operational amplifier, and then inject it into the system through an injection circuit, thereby effectively reducing the size, but the bandwidth requirements for active devices are high, and the cost is high. It also requires an additional isolated power supply.

[0004] In the prior art, with the rise of digital control technology, digital active EMI filtering technology is obtained by combining digital control with active EMI filters, such as Fig.12 As shown, its core principle is the same as the traditional active EMI filtering technology, except that the active devices are replaced by digital controllers, an analog-to-digital converter (ADC) is added to the detection loop, and a digital-to-analog converter (DAC) is added to the injection loop, thereby reducing costs and size.

[0005] However, in the above-mentioned digital active EMI filtering technology, the ADC in the detection loop and the DAC in the injection loop still require relatively high costs, and in order to improve the EMI suppression effect, a decoupling inductor needs to be added between the detection point and the injection point of the circuit, thereby further increasing the volume. At the same time, the existing digital active EMI filtering technology usually performs interference suppression on the positive bus and the negative bus, resulting in the inability to fully utilize the EMI suppression capability, as well as the mutual conversion between common-mode interference and differential-mode interference.

[0006] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0007] In response to the above problems, the present application provides a current-type digital active EMI filtering method and circuit based on switching spectrum analysis and reconstruction, which is suitable for scenarios dominated by common-mode noise. It can achieve composite suppression of common mode and differential mode while reducing the volume and continuously optimize the EMI suppression effect through iterative updates.

[0008] To achieve the purpose of this application, this application provides the following technical solutions:

[0009] In a first aspect, the present application provides a current-mode digital active EMI filtering method based on switch spectrum analysis and reconstruction, comprising:

[0010] Acquire initial common-mode noise data and initial differential-mode noise data of the buck circuit under test at the switching frequency point; the initial common-mode noise data includes initial common-mode noise spectrum amplitude data and phase data, and the initial differential-mode noise data includes initial differential-mode noise spectrum amplitude data and phase data;

[0011] Constructing a common-mode equivalent circuit and a differential-mode equivalent circuit including a noise source, a compensation voltage source, a compensation capacitor, a parasitic capacitor and a linear impedance stabilization network (LISN) impedance, and calculating the initial compensation voltage common-mode data and the initial compensation voltage differential-mode data of each frequency point according to the initial common-mode noise data and the initial differential-mode noise data to obtain the initial compensation voltage data; the initial compensation voltage data includes: the initial compensation voltage common-mode data and the initial compensation voltage differential-mode data, the initial compensation voltage common-mode data includes: initial compensation voltage common-mode frequency spectrum amplitude data and phase data, the initial compensation voltage differential-mode data includes: initial compensation voltage differential-mode frequency spectrum amplitude data and phase data;

[0012] The initial compensation voltage data is outputted synchronously with pulse width modulation (PWM) through DAC to perform initial noise compensation; wherein the initial compensation voltage common mode data is outputted to the common mode compensation capacitor to generate an initial common mode compensation current inputted into the ground line to compensate for the common mode noise, and the initial compensation voltage differential mode data is outputted to the differential mode compensation capacitor to generate an initial differential mode compensation current inputted into the positive bus to compensate for the differential mode noise;

[0013] After the initial noise compensation is completed, the noise voltage on the LISN is measured as the noise source voltage, and secondary compensation voltage data is calculated and superimposed on the initial compensation voltage data to iterate the compensation voltage data.

[0014] In a possible implementation, the step of obtaining initial common-mode noise data and initial differential-mode noise data of the Buck circuit at a switching frequency point includes:

[0015] The common mode noise voltage time domain waveform data and the differential mode noise voltage time domain waveform data on the LISN are measured by a noise separator and an oscilloscope;

[0016] The initial common mode noise data and the initial differential mode noise data at the switching frequency point are obtained by fast Fourier transform (FFT) according to the common mode noise voltage time domain waveform data and the differential mode noise voltage time domain waveform data.

[0017] In a possible implementation, the step of measuring the common mode noise voltage time domain waveform data and the differential mode noise voltage time domain waveform data on the LISN through a noise separator and an oscilloscope includes:

[0018] The common mode noise on the LISN is separated from the differential mode noise by a noise separator;

[0019] The common-mode noise voltage time-domain waveform data and the differential-mode noise voltage time-domain waveform data are obtained by measuring with an oscilloscope according to the separated common-mode noise and the differential-mode noise.

[0020] In a possible implementation, the step of constructing a common-mode equivalent circuit and a differential-mode equivalent circuit including a noise source, a compensation voltage source, a compensation capacitor, a parasitic capacitor, and a LISN impedance, and calculating initial compensation voltage common-mode data and initial compensation voltage differential-mode data of each frequency point according to the initial common-mode noise data and the initial differential-mode noise data to obtain initial compensation voltage data includes:

[0021] Constructing the common-mode equivalent circuit and the differential-mode equivalent circuit including a noise source, a compensation voltage source, a compensation capacitor, a parasitic capacitor and a LISN impedance;

[0022] Ignoring the parasitic capacitance of the order of picofarad, the relationship between the common-mode data of the equivalent model compensation voltage and the common-mode data of the equivalent model noise source voltage is obtained according to the superposition and cancellation principle, and the first formula is constructed;

[0023] According to the superposition and cancellation principle, the relationship between the differential mode data of the equivalent model compensation voltage and the differential mode data of the equivalent model noise source voltage is obtained, and the second formula is constructed;

[0024] Calculate the common-mode compensation voltage amplitude and phase required at each switching frequency point according to the first formula, and calculate the differential-mode compensation voltage amplitude and phase required at each switching frequency point according to the second formula;

[0025] The common-mode compensation voltage amplitude and phase sine waves of each switching frequency point are superimposed to obtain the initial compensation voltage common-mode data, and the differential-mode compensation voltage amplitude and phase sine waves of each switching frequency point are superimposed to obtain the initial compensation voltage differential-mode data.

[0026] In a possible implementation, the first formula is:

[0027] ;

[0028] in, is the common-mode compensation voltage amplitude, is the common mode compensation voltage phase, is the LISN equivalent resistance, is the LISN equivalent impedance, is the impedance of the common-mode compensation capacitor, is the common mode noise source voltage amplitude, is the common mode noise source voltage phase;

[0029] The second formula is:

[0030] ;

[0031] in, is the differential mode compensation voltage amplitude, is the differential mode compensation voltage phase, is the impedance of the input capacitor in the differential mode equivalent circuit, is the impedance of the common-mode compensation capacitor, is the voltage amplitude of the differential mode noise source, is the voltage phase of the differential mode noise source.

[0032] In a possible implementation, the common-mode compensation voltage amplitude and phase at each switching frequency point are sinusoidally superimposed using a third formula, and the third formula is:

[0033] ;

[0034] in, is the initial compensation voltage common mode data, is the switching frequency, For time;

[0035] The differential mode compensation voltage amplitude and phase of each switching frequency point are sinusoidally superimposed by a fourth formula, and the fourth formula is:

[0036] ;

[0037] in, is the initial compensation voltage differential mode data.

[0038] In a possible implementation, the step of outputting the initial compensation voltage data synchronously with PWM through a DAC to perform initial noise compensation includes:

[0039] The compensation voltage reference point is set as the negative bus through the common mode equivalent circuit and the differential mode equivalent circuit;

[0040] Outputting the initial compensation voltage common mode data to the common mode compensation capacitor, generating an initial common mode compensation current input to the ground line, and compensating for the common mode noise;

[0041] The initial compensation voltage differential mode data is output to the differential mode compensation capacitor to generate an initial differential mode compensation current which is input to the positive bus to compensate for the differential mode noise.

[0042] In one possible implementation, the starting time of the initial compensation voltage common-mode data output is aligned with the starting time of the initial common-mode noise data, and the starting time of the initial compensation voltage differential-mode data output is aligned with the starting time of the initial differential-mode noise data, that is, the time when the starting point of the measured common-mode and differential-mode noise data corresponds to PWM is the synchronous output point of the compensation voltage and PWM.

[0043] In a possible implementation, after the initial noise compensation is completed, the noise voltage on the LISN is measured as the noise source voltage, secondary compensation voltage data is calculated, and superimposed on the initial compensation voltage data. The step of iterating the compensation voltage data includes:

[0044] After the initial noise compensation is completed, measuring the noise voltage on the LISN as the noise source voltage;

[0045] Obtain secondary common-mode noise data and secondary differential-mode noise data through the noise source voltage;

[0046] Calculate the secondary compensation voltage common mode data and the secondary compensation voltage differential mode data of each frequency point according to the secondary common mode noise data and the secondary differential mode noise data to obtain the secondary compensation voltage data;

[0047] After the secondary compensation voltage data is superimposed on the initial compensation voltage data, the data is output synchronously with the PWM through the DAC to perform secondary noise compensation.

[0048] In a second aspect, the present application further provides a current-type digital active EMI filter circuit based on switch spectrum analysis and reconstruction, which is used to perform the above-mentioned current-type digital active EMI filter method based on switch spectrum analysis and reconstruction, and the circuit includes an injection circuit and a digital control circuit;

[0049] The digital control circuit is connected to the device under test (EUT) through an injection circuit, and includes a digital controller connected to two DACs; the digital controller is used to drive the switch tube, and is used to obtain the common-mode noise data and the differential-mode noise data of the buck circuit under test at the switching frequency point, and is used to calculate the compensation voltage common-mode data and the compensation voltage differential-mode data of each frequency point according to the common-mode noise data and the differential-mode noise data to obtain the compensation voltage data, and is used to perform compensation voltage superposition, and is used to control PWM and the DAC output synchronization; the DAC is used to perform analog output of the compensation voltage data;

[0050] The injection circuit includes a common-mode compensation capacitor and a differential-mode compensation capacitor. The common-mode compensation capacitor is used to generate a common-mode compensation current input to a ground line through the compensation voltage common-mode data to compensate for common-mode noise; the differential-mode compensation capacitor is used to generate a differential-mode compensation current input to a positive bus through the compensation voltage differential-mode data to compensate for differential-mode noise.

[0051] The technical solution provided by this application may have the following beneficial effects:

[0052] The present application provides a method and circuit for reconstructing current-type digital active EMI filtering based on switching spectrum analysis, which is suitable for scenarios dominated by common-mode noise, does not require a detection circuit, and can reduce costs while reducing volume; at the same time, the EMI suppression capability is fully utilized to achieve composite suppression of common-mode and differential-mode interference, avoid mutual conversion between common-mode interference and differential-mode interference, and optimize the EMI suppression effect through continuous iteration. After a single iteration, the common-mode noise in the low-frequency band drops by 10-30dB, and the differential-mode noise drops by 10-40dB. After two iterations, the common-mode noise spectrum drops by 20-30dB in the low-frequency band, and the differential-mode noise spectrum drops by 20-40dB.

[0053] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure. For those of ordinary skill in the art, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0055] Figure 1 A schematic diagram of a flow chart of a current-mode digital active EMI filtering method based on switch spectrum analysis and reconstruction provided in an embodiment of the present application;

[0056] Figure 2 A flow chart of step S100 of a method for reconstructing a current-mode digital active EMI filter based on switch spectrum analysis provided in an embodiment of the present application;

[0057] Figure 3 A flow chart of step S200 of a method for reconstructing a current-mode digital active EMI filter based on switch spectrum analysis provided in an embodiment of the present application;

[0058] Figure 4 A flow chart of step S300 of a method for reconstructing a current-mode digital active EMI filter based on switch spectrum analysis provided in an embodiment of the present application;

[0059] Figure 5 A flow chart of step S400 of a method for reconstructing current-mode digital active EMI filtering based on switch spectrum analysis provided in an embodiment of the present application;

[0060] Figure 6 A logic schematic diagram of a current-mode digital active EMI filtering method based on switch spectrum analysis and reconstruction provided in an embodiment of the present application;

[0061] Figure 7 A schematic diagram of a common-mode equivalent circuit model of a current-type digital active EMI filtering method based on switching spectrum analysis and reconstruction provided in an embodiment of the present application;

[0062] Figure 8 A schematic diagram of a differential mode equivalent circuit model of a current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction provided in an embodiment of the present application;

[0063] Fig. 9 A common simulation spectrum effect diagram of a current-mode digital active EMI filtering method based on switch spectrum analysis and reconstruction provided in an embodiment of the present application;

[0064] Fig.10 A differential simulation spectrum effect diagram of a current-mode digital active EMI filtering method based on switch spectrum analysis and reconstruction provided in an embodiment of the present application;

[0065] Fig.11 A schematic diagram of the structure of a current-type digital active EMI filter circuit based on switch spectrum analysis and reconstruction provided in an embodiment of the present application;

[0066] Fig.12 This is a schematic diagram of the circuit structure of the existing digital active EMI filtering technology in the background technology of this application. DETAILED DESCRIPTION

[0067] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the disclosure will be more comprehensive and complete and to fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0068] In this example implementation, a method for dynamic interference power management based on switching spectrum analysis and reconstruction of current-type digital active EMI filtering is first provided under the conditions of sparse feedback and missing observation. Figure 1 As shown in , the current-mode digital active EMI filtering method based on switch spectrum analysis and reconstruction may include the following steps:

[0069] Step S100: obtaining initial common-mode noise data and initial differential-mode noise data of the Buck circuit at a switching frequency point; the initial common-mode noise data includes initial common-mode noise spectrum amplitude data and phase data, and the initial differential-mode noise data includes initial differential-mode noise spectrum amplitude data and phase data.

[0070] Step S200: construct a common-mode equivalent circuit and a differential-mode equivalent circuit including a noise source, a compensation voltage source, a compensation capacitor, a parasitic capacitor and a LISN impedance, and calculate the initial compensation voltage common-mode data and the initial compensation voltage differential-mode data of each frequency point according to the initial common-mode noise data and the initial differential-mode noise data to obtain the initial compensation voltage data; the initial compensation voltage data includes: the initial compensation voltage common-mode data and the initial compensation voltage differential-mode data, the initial compensation voltage common-mode data includes: the initial compensation voltage common-mode spectrum amplitude data and phase data, and the initial compensation voltage differential-mode data includes: the initial compensation voltage differential-mode spectrum amplitude data and phase data.

[0071] Step S300: The initial compensation voltage data is output synchronously with the PWM through the DAC to perform initial noise compensation; wherein, the initial compensation voltage common-mode data is output to the common-mode compensation capacitor to generate an initial common-mode compensation current input to the ground line to compensate for common-mode noise, and the initial compensation voltage differential-mode data is output to the differential-mode compensation capacitor to generate an initial differential-mode compensation current input to the positive bus to compensate for differential-mode noise.

[0072] Step S400: After the initial noise compensation is completed, the noise voltage on the LISN is measured as the noise source voltage, and secondary compensation voltage data is calculated and superimposed on the initial compensation voltage data to iterate the compensation voltage data.

[0073] The above-mentioned current-type digital active EMI filtering method based on switching spectrum analysis and reconstruction is suitable for scenarios dominated by common-mode noise. It can generate a common-differential mode composite compensation voltage and inject it into the compensation capacitor synchronously with the DAC, convert it into a compensation current input into the positive bus and ground line for noise compensation. The traditional detection circuit and decoupling inductor are omitted, the size is reduced, and the cost is reduced; at the same time, Figure 9-10 As shown, after a single iteration, the common mode noise in the low and middle frequency bands can be reduced by 10-30dB, and the differential mode noise can be reduced by 10-40dB. After two iterations, the common mode noise spectrum in the low and middle frequency bands can be reduced by 20-30dB, and the differential mode noise spectrum can be reduced by 20-40dB.

[0074] Next, we will refer to Figures 2 to 6 The steps of the above-mentioned method for reconstructing current-type digital active EMI filtering based on switching spectrum analysis in this example implementation are described in more detail. Figure 6 The L line is the positive busbar and the PE line is the ground line.

[0075] In step S100, initial common-mode noise data and initial differential-mode noise data of the Buck circuit at the switching frequency are obtained; the initial common-mode noise data includes initial common-mode noise spectrum amplitude data and phase data, and the initial differential-mode noise data includes initial differential-mode noise spectrum amplitude data and phase data.

[0076] It should be noted that the initial common-mode noise data and the initial differential-mode noise data are the noise data of a single iteration at the switching frequency of the Buck circuit, that is, the noise voltage of the Buck circuit on the measurement LISN, and the Buck circuit is the device under test (EUT), that is, the buck circuit under test. At the same time, to obtain the initial common-mode noise data and the initial differential-mode noise data, a simulation circuit can be constructed through simulation software such as MATLAB and PSIM, and then the noise voltage on the simulation circuit LISN can be measured, and finally the initial common-mode noise data and the initial differential-mode noise data can be obtained through noise voltage separation.

[0077] In a possible implementation, step S100 may further include the following sub-steps:

[0078] In step S110 , the common mode noise voltage time domain waveform data and the differential mode noise voltage time domain waveform data on the LISN are measured by a noise separator and an oscilloscope.

[0079] In step S120, the initial common-mode noise data and the initial differential-mode noise data at the switching frequency are obtained through FFT according to the common-mode noise voltage time-domain waveform data and the differential-mode noise voltage time-domain waveform data.

[0080] It should be noted that FFT greatly reduces the amount of DFT calculations through specific algorithm structures (such as butterfly operations, etc.), thereby quickly converting time domain waveform data into frequency domain data. In the above scenario, FFT can be used to convert the common-mode and differential-mode noise voltage time domain waveform data collected by the oscilloscope into frequency domain data, and then obtain the common-mode and differential-mode noise data at the switching frequency point, which is convenient for analyzing the characteristics of noise at specific frequency points.

[0081] Furthermore, step S110 may include:

[0082] In step S111 , the common mode noise and the differential mode noise on the LISN are separated by a noise separator.

[0083] It should be noted that the noise separator mainly works based on the impedance characteristics of the circuit and Kirchhoff's law. Taking the common mode and differential mode signal separation of the present application as an example, under the equivalent circuit model, the working principle formula is:

[0084] ;

[0085] in, is the common mode noise voltage, is the differential mode noise voltage, is the noise voltage from the positive bus to the ground, is the noise voltage from the negative bus to the ground.

[0086] In step S112, the common mode noise voltage time domain waveform data and the differential mode noise voltage time domain waveform data are obtained by measuring with an oscilloscope according to the separated common mode noise and the differential mode noise.

[0087] In step S200, a common-mode equivalent circuit and a differential-mode equivalent circuit including a noise source, a compensation voltage source, a compensation capacitor, a parasitic capacitor and a LISN impedance are constructed, and the initial compensation voltage common-mode data and the initial compensation voltage differential-mode data of each frequency point are calculated according to the initial common-mode noise data and the initial differential-mode noise data to obtain the initial compensation voltage data.

[0088] It should be noted that the initial compensation voltage data includes: the initial compensation voltage common mode data and the initial compensation voltage differential mode data; the initial compensation voltage common mode data includes: the initial compensation voltage common mode spectrum amplitude data and phase data; the initial compensation voltage differential mode data includes: the initial compensation voltage differential mode spectrum amplitude data and phase data.

[0089] In a possible implementation, step S200 may further include the following sub-steps:

[0090] In step S210, the common-mode equivalent circuit and the differential-mode equivalent circuit including a noise source, a compensation voltage source, a compensation capacitor, a parasitic capacitor and a LISN impedance are constructed.

[0091] It should be noted that the common mode equivalent circuit and the differential mode equivalent circuit can be Figure 7-8 As shown in the figure, by abstracting the noise source, compensation capacitor, parasitic capacitor, LISN impedance and other components in the actual circuit into a mathematical model, a simplified framework is provided for theoretical analysis, avoiding complex actual circuit debugging.

[0092] In step S220, the parasitic capacitance of the order of picofarad is ignored, and the relationship between the common-mode data of the equivalent model compensation voltage and the common-mode data of the equivalent model noise source voltage is obtained according to the superposition and cancellation principle to construct a first formula.

[0093] It should be noted that, ignoring the parasitic capacitance of the order of picofarads, such as , , , retain the main impedance and .

[0094] In step S230, the relationship between the equivalent model compensation voltage differential mode data and the equivalent model noise source voltage differential mode data is obtained according to the superposition cancellation principle, and a second formula is constructed.

[0095] In step S240, the common-mode compensation voltage amplitude and phase required at each switching frequency point are calculated according to the first formula, and the differential-mode compensation voltage amplitude and phase required at each switching frequency point are calculated according to the second formula.

[0096] In step S250, the common-mode compensation voltage amplitude and phase sine waves of each switching frequency point are superimposed to obtain the initial compensation voltage common-mode data, and the differential-mode compensation voltage amplitude and phase sine waves of each switching frequency point are superimposed to obtain the initial compensation voltage differential-mode data.

[0097] It should be noted that, for example, the switching frequency , then the switching frequency includes , , wait.

[0098] Furthermore, the first formula is:

[0099] ;

[0100] in, is the common-mode compensation voltage amplitude, is the common mode compensation voltage phase, is the LISN equivalent resistance, is the LISN equivalent impedance, is the impedance of the common-mode compensation capacitor, is the common mode noise source voltage amplitude, is the common-mode noise source voltage phase.

[0101] The second formula is:

[0102] ;

[0103] in, is the differential mode compensation voltage amplitude, is the differential mode compensation voltage phase, is the impedance of the input capacitor in the differential mode equivalent circuit, is the impedance of the common-mode compensation capacitor, is the voltage amplitude of the differential mode noise source, is the voltage phase of the differential mode noise source.

[0104] It should be noted that , , , ,in, is the common mode compensation capacitor, is the differential mode compensation capacitor, is the internal capacitance of LISN, are other capacitors in the differential mode equivalent circuit.

[0105] Furthermore, the common-mode compensation voltage amplitude and phase at each switching frequency point are sinusoidally superimposed by a third formula, and the third formula is:

[0106] ;

[0107] in, is the initial compensation voltage common mode data, is the switching frequency, For time;

[0108] The differential mode compensation voltage amplitude and phase of each switching frequency point are sinusoidally superimposed by a fourth formula, and the fourth formula is:

[0109] ;

[0110] in, is the initial compensation voltage differential mode data.

[0111] In step S300, the initial compensation voltage data is output synchronously with the PWM through the DAC to perform initial noise compensation; wherein, the initial compensation voltage common-mode data is output to the common-mode compensation capacitor to generate an initial common-mode compensation current input to the ground line to compensate for common-mode noise, and the initial compensation voltage differential-mode data is output to the differential-mode compensation capacitor to generate an initial differential-mode compensation current input to the positive bus to compensate for differential-mode noise.

[0112] It should be noted that common-mode noise is the in-phase interference between the positive / negative bus and the ground line. The common-mode noise can be offset by adjusting the voltage of the ground line (relative to the negative bus). Differential-mode noise is the potential difference between the positive bus and the negative bus. The compensation voltage directly injected into the positive bus can offset the interference. In this way, the phase shift caused by multiple reference points can be avoided.

[0113] Optionally, the DAC may adopt a DAC with dual output terminals or use two DACs.

[0114] In a possible implementation, step S300 may further include the following sub-steps:

[0115] In step S310, the compensation voltage reference point is set to the negative bus through the common mode equivalent circuit and the differential mode equivalent circuit.

[0116] In step S320, the initial compensation voltage common mode data is output to the common mode compensation capacitor to generate an initial common mode compensation current input to the ground line to compensate for the common mode noise.

[0117] In step S330, the initial compensation voltage differential mode data is output to the differential mode compensation capacitor to generate an initial differential mode compensation current which is input to the positive bus to compensate for the differential mode noise.

[0118] It should be noted that the starting time of the initial compensation voltage common mode data output is aligned with the starting time of the initial common mode noise data, and the starting time of the initial compensation voltage differential mode data output is aligned with the starting time of the initial differential mode noise data. That is, the time when the starting point of the measured common mode and differential mode noise data corresponds to PWM is the synchronous output point of the compensation voltage and PWM.

[0119] It can be understood that the time when the starting point of the measured common-mode and differential-mode noise data corresponds to the PWM is the synchronous output point of the compensation voltage output and the PWM.

[0120] In step S400, after the initial noise compensation is completed, the noise voltage on the LISN is measured as the noise source voltage, and secondary compensation voltage data is calculated and superimposed on the initial compensation voltage data to iterate the compensation voltage data.

[0121] It should be noted that by repeating the method of S100-S300 and iterating the compensation voltage, the EMI suppression effect is further improved.

[0122] In a possible implementation, step S400 may further include the following sub-steps:

[0123] In step S410, after the initial noise compensation is completed, the noise voltage on the LISN is measured as the noise source voltage.

[0124] In step S420 , secondary common-mode noise data and secondary differential-mode noise data are obtained through the noise source voltage.

[0125] In step S430, secondary compensation voltage common mode data and secondary compensation voltage differential mode data of each frequency point are calculated according to the secondary common mode noise data and the secondary differential mode noise data to obtain secondary compensation voltage data.

[0126] In step S440, the secondary compensation voltage data is superimposed on the initial compensation voltage data and then outputted synchronously with PWM through DAC to perform secondary noise compensation.

[0127] It should be noted that if there is a delay or asynchronism in the compensation voltage, the compensation voltage can be reconstructed by adjusting the compensation voltage data sequence to eliminate the delay. The specific method can be to actually test the time difference between the PWM signal and the DAC output compensation voltage. ; Move the first n data in the compensation voltage array to the end of the array to advance the compensation voltage phase , aligned with the noise source.

[0128] Furthermore, in this exemplary embodiment, a current-mode digital active EMI filter circuit based on switch spectrum analysis and reconstruction is provided, which is used to perform the above-mentioned current-mode digital active EMI filter method based on switch spectrum analysis and reconstruction. Fig.11 As shown in , the circuit may include an injection circuit and a digital control circuit.

[0129] The digital control circuit is connected to the EUT through an injection circuit, and includes a digital controller connected to two DACs; the digital controller is used to drive the switch tube, and is used to obtain the common-mode noise data and the differential-mode noise data of the buck circuit under test at the switching frequency point, and is used to calculate the compensation voltage common-mode data and the compensation voltage differential-mode data of each frequency point according to the common-mode noise data and the differential-mode noise data to obtain the compensation voltage data, and is used to perform compensation voltage superposition, and is used to control PWM and the DAC output synchronization; the DAC is used to analog output the compensation voltage data.

[0130] The injection circuit includes a common-mode compensation capacitor and a differential-mode compensation capacitor. The common-mode compensation capacitor is used to generate a common-mode compensation current input to a ground line through the compensation voltage common-mode data to compensate for common-mode noise; the differential-mode compensation capacitor is used to generate a differential-mode compensation current input to a positive bus through the compensation voltage differential-mode data to compensate for differential-mode noise.

[0131] It should be noted that the common mode noise data and the differential mode noise data can be stored in the digital controller in advance, such as Fig.11 As shown, the LISN contains a power supply Resistors in series ,inductance With capacitor , The low-pass filter and LISN impedance , used for impedance matching to ensure EMI measurement accuracy. The injection circuit includes common-mode compensation capacitors Differential mode compensation capacitor , Connect to PE to inject common-mode compensation current. Connected to the positive busbar to inject differential mode compensation current, the reference point of the two capacitors is the implicitly connected neutral line negative busbar, and works under the drive of the digital control circuit. The buck circuit under test includes: switch tube and , Switching tube parasitic capacitance , , Node switch , Connect inductor , Input Capacitance Output Capacitor ,load , Parasitic capacitance of the positive and negative busbars at the output end to the ground and , parasitic capacitance and drive ; control and Alternate conduction to achieve the voltage reduction function. is the parasitic capacitance between the switch node and the ground line; when the switch tube is turned on or off, The point voltage changes at high frequency, through The common mode noise current is coupled to the ground line, becoming an EMI source. The digital control circuit has a digital controller connected to two DACs, and the two DACs are used to output common mode and differential mode compensation voltages respectively.

[0132] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present disclosure are indicated by the appended claims.

[0133] The above embodiments are only used to illustrate the technical solution of the present application, but not to limit it. The present application is not limited to the exact structure described above and illustrated in the accompanying drawings, and it cannot be determined that the specific implementation of the present application is limited to these descriptions. For ordinary technicians in the technical field to which the present application belongs, various changes and modifications made without departing from the concept of the present application should be deemed to belong to the protection scope of the present application.

Claims

1. A current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction, characterized in that: include: Obtain the initial common-mode noise data and initial differential-mode noise data of the Buck circuit at the switching frequency point; The initial common mode noise data includes initial common mode noise spectrum amplitude data and phase data, and the initial differential mode noise data includes initial differential mode noise spectrum amplitude data and phase data; Constructing a common-mode equivalent circuit and a differential-mode equivalent circuit including a noise source, a compensation voltage source, a compensation capacitor, a parasitic capacitor and a LISN impedance, and calculating initial compensation voltage common-mode data and initial compensation voltage differential-mode data of each frequency point according to the initial common-mode noise data and the initial differential-mode noise data to obtain initial compensation voltage data; The initial compensation voltage data includes: the initial compensation voltage common mode data and the initial compensation voltage differential mode data, the initial compensation voltage common mode data includes: initial compensation voltage common mode spectrum amplitude data and phase data, the initial compensation voltage differential mode data includes: initial compensation voltage differential mode spectrum amplitude data and phase data; The initial compensation voltage data is output synchronously with PWM through DAC to perform initial noise compensation; wherein, the initial compensation voltage common mode data is output to the common mode compensation capacitor to generate an initial common mode compensation current input to the ground line to compensate for the common mode noise, and the initial compensation voltage differential mode data is output to the differential mode compensation capacitor to generate an initial differential mode compensation current input to the positive bus to compensate for the differential mode noise; After the initial noise compensation is completed, the noise voltage on the LISN is measured as the noise source voltage, and secondary compensation voltage data is calculated and superimposed on the initial compensation voltage data to iterate the compensation voltage data.

2. The current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction according to claim 1 is characterized in that: The step of obtaining initial common-mode noise data and initial differential-mode noise data of the Buck circuit at a switching frequency point includes: The common mode noise voltage time domain waveform data and the differential mode noise voltage time domain waveform data on the LISN are measured by a noise separator and an oscilloscope; The initial common-mode noise data and the initial differential-mode noise data at the switching frequency are obtained through FFT according to the common-mode noise voltage time-domain waveform data and the differential-mode noise voltage time-domain waveform data.

3. The current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction according to claim 2 is characterized in that: The step of measuring the common mode noise voltage time domain waveform data and the differential mode noise voltage time domain waveform data on the LISN through a noise separator and an oscilloscope comprises: The common mode noise on the LISN is separated from the differential mode noise by a noise separator; The common-mode noise voltage time-domain waveform data and the differential-mode noise voltage time-domain waveform data are obtained by measuring with an oscilloscope according to the separated common-mode noise and the differential-mode noise.

4. The current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction according to claim 1 is characterized in that: The step of constructing a common-mode equivalent circuit and a differential-mode equivalent circuit including a noise source, a compensation voltage source, a compensation capacitor, a parasitic capacitor and a LISN impedance, and calculating initial compensation voltage common-mode data and initial compensation voltage differential-mode data of each frequency point according to the initial common-mode noise data and the initial differential-mode noise data to obtain initial compensation voltage data includes: Constructing the common-mode equivalent circuit and the differential-mode equivalent circuit including a noise source, a compensation voltage source, a compensation capacitor, a parasitic capacitor and a LISN impedance; Ignoring the parasitic capacitance of the order of picofarad, the relationship between the common-mode data of the equivalent model compensation voltage and the common-mode data of the equivalent model noise source voltage is obtained according to the superposition and cancellation principle, and the first formula is constructed; According to the superposition and cancellation principle, the relationship between the differential mode data of the equivalent model compensation voltage and the differential mode data of the equivalent model noise source voltage is obtained, and the second formula is constructed; Calculate the common-mode compensation voltage amplitude and phase required at each switching frequency point according to the first formula, and calculate the differential-mode compensation voltage amplitude and phase required at each switching frequency point according to the second formula; The common-mode compensation voltage amplitude and phase sine waves of each switching frequency point are superimposed to obtain the initial compensation voltage common-mode data, and the differential-mode compensation voltage amplitude and phase sine waves of each switching frequency point are superimposed to obtain the initial compensation voltage differential-mode data.

5. The current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction according to claim 4 is characterized in that: The first formula is: ； in, is the common-mode compensation voltage amplitude, is the common mode compensation voltage phase, is the LISN equivalent resistance, is the LISN equivalent impedance, is the impedance of the common-mode compensation capacitor, is the common mode noise source voltage amplitude, is the common mode noise source voltage phase; The second formula is: ； in, is the differential mode compensation voltage amplitude, is the differential mode compensation voltage phase, is the impedance of the input capacitor in the differential mode equivalent circuit, is the impedance of the common-mode compensation capacitor, is the voltage amplitude of the differential mode noise source, is the voltage phase of the differential mode noise source.

6. The current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction according to claim 4 is characterized in that: The common-mode compensation voltage amplitude and phase at each switching frequency point are sinusoidally superimposed by a third formula, and the third formula is: ； in, is the initial compensation voltage common mode data, is the switching frequency, For time; The differential mode compensation voltage amplitude and phase of each switching frequency point are sinusoidally superimposed by a fourth formula, and the fourth formula is: ； in, is the initial compensation voltage differential mode data.

7. The current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction according to claim 1 is characterized in that: The step of outputting the initial compensation voltage data synchronously with PWM through DAC to perform initial noise compensation includes: The compensation voltage reference point is set as the negative bus through the common mode equivalent circuit and the differential mode equivalent circuit; Outputting the initial compensation voltage common mode data to the common mode compensation capacitor, generating an initial common mode compensation current input to the ground line, and compensating for the common mode noise; The initial compensation voltage differential mode data is output to the differential mode compensation capacitor to generate an initial differential mode compensation current which is input to the positive bus to compensate for the differential mode noise.

8. The current-mode digital active EMI filtering method based on switch spectrum analysis and reconstruction according to claim 7 is characterized in that: The starting time of the initial compensation voltage common-mode data output is aligned with the starting time of the initial common-mode noise data, and the starting time of the initial compensation voltage differential-mode data output is aligned with the starting time of the initial differential-mode noise data, that is, the time when the starting point of the measured common-mode and differential-mode noise data corresponds to PWM is the synchronous output point of the compensation voltage and PWM.

9. The current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction according to claim 1 is characterized in that: After the initial noise compensation is completed, the noise voltage on the LISN is measured as the noise source voltage, and secondary compensation voltage data is calculated and superimposed on the initial compensation voltage data. The step of iterating the compensation voltage data includes: After the initial noise compensation is completed, measuring the noise voltage on the LISN as the noise source voltage; Obtain secondary common-mode noise data and secondary differential-mode noise data through the noise source voltage; Calculate the secondary compensation voltage common mode data and the secondary compensation voltage differential mode data of each frequency point according to the secondary common mode noise data and the secondary differential mode noise data to obtain the secondary compensation voltage data; After the secondary compensation voltage data is superimposed on the initial compensation voltage data, the data is output synchronously with the PWM through the DAC to perform secondary noise compensation.

10. A current-type digital active EMI filter circuit based on switching spectrum analysis and reconstruction, characterized in that: The circuit is used to perform the current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction as described in any one of claims 1 to 9, and the circuit includes an injection circuit and a digital control circuit; The digital control circuit is connected to the EUT through an injection circuit, and includes a digital controller connected to two DACs; the digital controller is used to drive the switch tube, and is used to obtain the common-mode noise data and the differential-mode noise data of the buck circuit under test at the switching frequency point, and is used to calculate the compensation voltage common-mode data and the compensation voltage differential-mode data of each frequency point according to the common-mode noise data and the differential-mode noise data to obtain the compensation voltage data, and is used to perform compensation voltage superposition, and is used to control PWM and the DAC output synchronization; The DAC is used to perform analog output of the compensation voltage data; The injection circuit includes a common-mode compensation capacitor and a differential-mode compensation capacitor, wherein the common-mode compensation capacitor is used to generate a common-mode compensation current input to a ground line through the compensation voltage common-mode data to compensate for common-mode noise; The differential mode compensation capacitor is used to generate a differential mode compensation current through the compensation voltage differential mode data and input it into the positive bus to compensate for differential mode noise.

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